Conventionally, the injection of an anesthesia or a drug into large animals living in the wild or in zoos, has been achieved by utilizing an injecting projectile fired from a rifle or handgun. Such projectiles may take the form of a hollow, cylindrical casing which is subdivided into a pressure chamber and a drug chamber with a piston sliding within the casing and with the drug chamber terminating in a hollow needle. Such projectiles are fired at a certain, safe distance from the animal and the drug contained in the projectile is driven from the drug chamber by expansion of the gas (air under pressure) upon the projectile needle entering the body of the animal shortly after impact of the projectile. The following U.S. Patents are representative of such projectiles:
U.S. Pat. No. Re. 25,279, Crockford et al PA1 U.S. Pat. No. 1,819,415, B. Harris PA1 U.S. Pat. No. 3,358,685, C. A. Murdoch PA1 U.S. Pat. No. 3,359,979, C. A. Murdoch PA1 U.S. Pat. No. 4,103,893, E. C. Walker PA1 U.S. Pat. No. 4,243,036, Ott
U.S. Pat. No. 4,103,893 discloses a tranquilizer dart in the form of a hollow tube defining a cylindrical chamber having a tapered forward end mounting a pointed, hollow needle. A conical valve bears against an annular seat in the chamber with a triggering pin extending through the needle and having a forward end projecting beyond the needle point. Tranquilizer liquid is contained in the chamber between the valve and a first, front plunger. A rear plunger is provided at the rear end of the chamber with rearward movement limited by a transversely insertable stop pin. After loading a tranquilizing liquid into the frontal chamber, forward of the first plunger, air captured between the first plunger and the second plunger is compressed by insertion of the rear plunger. Upon impact, the triggering pin recedes, unsealing the conical valve and the expansion of the compressed air in the compressed air chamber forces the front plunger forward to inject the liquid into the animal.
U.S. Pat. No. 4,243,036 is directed to an automatically acting injection projectile which consists of a tubular casing bearing a slidable plunger and separating the interior of the casing into a rear gas chamber and a front anesthesia or drug chamber. A hollow needle projects forwardly of the tubular casing, a deformable tubular projectile brake surrounds the needle and the needle includes a radial outlet behind the needle point which is surrounded by a movable sliding sleeve. Upon impact with the body of the animal, the brake deforms and is pushed back along with the sleeve exposing the radial outlet of the hollow needle. The gas propellant drives the plunger to force the drug from the drug chamber through the hollow needle and into the surrounding tissue of the animal through the outlet.
While such systems have operated adequately in the past, and are indeed necessary because of the inability to closely approach wild animals, the same is not true for domestic animals. Irrespective of whether domestic animals or wild animals are to be injected, the use of a rifle or handgun fired automatic injecting projectiles is hampered by the single gas charge for the projectile and even though projectiles have been manufactured permitting a recharging of the gas chamber and the drug chamber, such recharging is difficult to achieve, particularly in the field.
Further, even where the large animals are of the domestic type such as cattle, sheep, etc. and can be readily approached, injection by single dosage, single use, hypodermic syringe projectiles, are beset by other problems such as premature injection of the drug during flight as a result of acceleration effect and inertia of the movable components.
It is therefore a primary object of the present invention to provide an extended length, pneumatic hypodermic syringe pole for use on animals which are readily approachable, such as domestic animals, or, on wild animals which are caged or otherwise restrained, which incorporates a large volume of pressurized gas capable of effecting multiple drug ejections, wherein the unit is easily handled, readily accepts prefilled syringes which can be quickly replaced and immediately used, wherein, the possibility of premature release of the drug is obviated and wherein, momentarily coupling of the pressurized gas source and the gas propulation chamber is automatically effected as a result of needle penetration of the body of the animal.